Comparative study at the cellular and subcellular levels of the adult male and female prostates of a unique species of rodent--Praomys (Mastomys) Natalensis--was made. The female possesses a well-developed prostate throughout life that may be considered homologous to the ventral prostatic lobe in the male Praomys. Histologically, only small differences exist to indicate that the female prostate is somewhat less active than the male (less secretion and the presence of fewer supranuclear light areas in the female than in the male prostate). At the electron microscopic level, within the female prostatic cells, there is less rough endoplasmic reticulum, and the number of secretory granules is lower than in the male. The arrangement of the cells, the organization of the subcellular structures, and the mode of secretion in both female and male prostates, however, are similar.